Common variable immunodeficiency (CVID) is a clinically heterogeneous disorder characterized by decreased serum immunoglobulin IgG and IgA levels. In addition to chronic or recurrent sinopulmonary infections, many patients develop gastrointestinal manifestations that can be disabling or fatal. Data suggest that these gut abnormalities have a primary immune basis, implicating T cells primarily, and are not related to the infectious complications of CVID. Currently there is no standard therapy for the associated gastrointestinal disease outside of empiric nutritional intervention for weight loss and non-specific anti-diarrheal agents. In addition there is no data about the prevalence of gastrointestinal abnormalities in CVID patients who have no overt gastrointestinal symptoms.